1. Field of the Invention
The present invention relates a bicycle front fork shock-absorbing structure and more particularly, to a hydraulic front fork that provides a locking function.
2. Description of the Related Art
A hydraulic type shock-absorbing front form for bicycle comprises an upper fork tube and a bottom fork tube axially coupled together, and a locking mechanism mounted on the inside. When the bicycle is moving over an uneven road surface to cause a relative movement between the upper fork tube and the lower fork tube, the internal hydraulic fluid is forced through the locking mechanism to change the flow path, thereby absorbing the shocks to provide a comfortable riding effect.
FIG. 1 shows a hydraulic front fork according to the prior art. According to this design, the front fork 1 has the inside space filled with a hydraulic fluid. Further, the front fork 1 comprises an upper fork tube 2, a bottom fork tube 3, a valve bush 4, which is fixedly mounted in the bottom side of the upper fork tube 2 and has one inlet 4a and two return-flow holes 4b, a flap 5 fastened to the bottom side of the valve bush 4 and adapted to cover the return-flow holes 4b, a needle valve 6, which is axially mounted in the upper fork tube 2 and has a conical front end 6a facing the top end of the inlet 4a and a rear end 6b extending out of the top end of the upper fork tube 2 for driving by an external force to adjust the pitch between the front end 6a and the top end of the inlet 4a and to further achieve changing of the flow rate and speed of the hydraulic fluid passing through the valve bush 4.
When the front end 6a is stopped against the inlet 4a to block the passage and when the upper fork tube 2 and the bottom fork tube 3 are moved relative to each other (i.e., the bicycle is moving over an uneven road surface), the needle valve 6 receives an impact force from the hydraulic fluid that flows upwards through the inlet 4a. Under the repeated impact effect of the hydraulic fluid, the connection area between the needle valve 6 and the upper fork tube 2 becomes loosened quickly.